Recently, magnetic resonance (MR) T2 and T1p relaxation time measurements have emerged as potential markers for early biochemical cartilage degeneration, and thus may be important when examining the pathogenesis of OA. Additionally, changes in kinematics, kinetics, spatiotemporal gait characteristics and functional activities have been reported in patients with early hip OA. The proposed study aims to investigate biochemical differences that may be seen in mild and moderate radiographic hip OA using MRI, exploring their relation to kinematics and function. It also aims to explore cartilage degeneration and progression of hip OA longitudinally, and establish the relationship between changes in composition and the development of morphological lesions. Our central hypothesis is that image-based measures of hip cartilage biochemical composition differs between controls and patients with hip OA, and are related to cartilage morphology, hip biomechanics, pain, function and severity of disease. To test this hypothesis, this study will 1) characterize hip cartilage composition (measured by MRI Tip and T2 relaxation times) in patients with hip OA, compared to controls, 2) determine the cross-sectional and longitudinal relationship between hip cartilage composition and morphology, and 3) determine whether hip cartilage composition is related to patient function (kinematics, kinetics, spatiotemporal gait characteristics, functional tests) and pain (WOMAC), both cross-sectionally and longitudinally. The results of the proposed study will help determine whether early biochemical degeneration in cartilage, as quantified by T2 and T1p mapping parameters, is associated with the progression of hip OA and is related to hip OA outcomes such as detriments in patient function. By evaluating the interrelationship between MR markers of compositional changes in OA and movement patterns during functional tasks, this study provides an essential link between tissue structure and function in the hip joint. In this proposal, an interdisciplinary team extends their extensive prior work in the knee, and to elucidate the complex interactions of abnormal movement patterns, cartilage biochemical and morphologic degeneration during the progression and outcomes of hip OA.